The present invention relates to a zigzag sewing machine and, more particularly, to a zigzag sewing machine equipped with a back stitch forming system capable of forming a plurality of back stitches before or after forming a pattern.
In this specification, the above-mentioned back stitch means forms such plural stitches while feeding the work slightly forward and backward without jogging the needle, at an end of main stitches forming a pattern.
In operating a conventional zigzag sewing machine equipped with such a back stitch forming system, back stitches are formed at a position corresponding to the present position of the needle in response to the operation of a back stitch control member. Therefore, during overcasting operation, the operator operates the back stitch control member to form back stitches in the work upon arrival of the needle over the work.
However, such a manner of operation of the zigzag sewing machine is troublesome because the back stitches must be formed in the work by operating the back stitch control member upon the arrival of the needle over the work.
Furthermore, if the back stitch control member is operated incorrectly while the needle is outside the work, the needle operates for stitching operation outside the work entangling the threads.
There is disclosed a zigzag sewing machine having a back stitch forming system in U.S. Pat. Nos. 3,977,338 and 4,345,532.